There is no USB / MP3 checkbox in my Insider settings. See the attached image.

It looks like you're not even connected to the amp, with your laptop, when you're actually connected, it will come up with a reload bar that updates everything every time you enter insider. If this bar isn't coming up, then you aren't connected.

When you have the correct or working USB cable, all of that stuff WILL come up, as far as the options in the image you have shown.